In general, when children join adults in group events such as domestic or foreign travel, mountain climbing, or an excursion, a leader has a considerable difficulty leading participants of the group event.
In detail, to lead many participants, the leader should not only know personal information about the participants but also build up an emergency contact network. If any participant is accidentally separated from the group, the leader should find the separated participant through the emergency contact network.
If the separated participant is an adult having a portable terminal such as a mobile phone, the adult can be easily found through the emergency contact network. However, if the separated participant is a child such as a kindergarten pupil or a primary-school pupil having no portable terminal, it is impossible to activate the emergency contact network in order to find the child. For this reason, if such kindergarten or primary-school pupils participate in an outdoor event in a group, it is necessary for a leader to lead them diligently. A slight absence of mind may frequently result in a child becoming lost.
For this reason, devices for preventing children from becoming lost have been disclosed in the related art. These devices are configured so that a child and his/her guardian conduct one-to-one communication rather than one-to-many (group) communication over a local area network. Here, the child and his/her guardian carry child loss prevention terminals, and these terminals conduct short distance wireless communication within a preset distance range. If the terminals of the child and his/her guardian deviate from the preset distance range during the short distance wireless communication, a warning sound is adapted to be output from the guardian's terminal. Thereby, the guardian is able to recognize that the child has become separated.
However, these devices are configured so that the child and his/her guardian conduct one-to-one short distance wireless communication. The short distance wireless communication has a disadvantage in that, when the child's terminal deviates from the preset distance range, the warning sound is output from only the guardian's terminal, and is not output from the child's terminal. Thus, the child may not recognize that his/her terminal has deviated from the preset distance range. Accordingly, the guardian experiences the inconvenience that he/she should go to find the child beyond the preset distance range when the warning sound is output from his/her terminal. These devices are unfit for a group meeting.